Engineering the optical response of a-Se thin films by employing morphological disorder

In this article, we experimentally demonstrate for the first time that photobleaching (PB) can be induced in morphologically disordered a-Se thin film, an observation which is opposite of the previously well-known photodarkening (PD) effects in morphologically ordered films. Further, the optical response of the film shows many fold increase with increase in control beam intensity. To explain the observed extraordinary phenomenon, we have proposed a model based on the morphological disorder of a modified surface and its subsequent photo-annealing. Our results demonstrate an efficient and yet simple new method to engineer the optical response of photosensitive thin films. We envision that this process can open up many avenues in optical field-enhanced absorption-based technologies.